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The last few weeks have seen substantial questioning of the quality of the analysis of the global climate record. This presentation, made to the top year at a local secondary school, looks at the Oxford climate series and shows how the way the data is presented may significantly affect judgments on how fast warming is occurring at one particular point on the earth’s surface. Apparently innocuous changes, such as varying the number of years in a moving average, can make substantial changes to the appearance of a temperature series. The notes to this presentation can be seen by downloading the PowerPoint file and clicking Notes Page in the View tab; or alternatively by downloading the PDF. Anybody wanting the raw data and the accompanying charts is very welcome to email Chris Goodall at chris@carboncommentary.com.

If your browser is not displaying the presentation properly in the embedded viewer above (Internet Explorer 7 and 8 users may encounter a problem depending on their settings), it is available for download in PowerPoint or PDF.

Copyright: Mat Hayward – Fotolia.com.

No climate data is without its critics. We do not have the equipment to measure the temperature in every square kilometre of the world’s surface so we cannot be sure that global ‘averages’ are correct. Disputes about the reliability of climate data will continue. But the US Government’s National Climatic Data Center (NCDC) is one of the world’s most authoritative sources of global data.

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Its temperature figures for January have just been reported (13 February). The month was unusually cold in the UK and in parts of the US. Some commentators, whose imagination fails to recognise that temperatures in central London or Washington DC are not typical of all parts of the world’s surface, had hypothesised that the 2008/2009 winter was particularly cold. Counter-evidence, such as the record-breaking highs in the state of Victoria in Australia was ignored.

The NCDC figures suggest that January was actually the 7th warmest on record. Let’s explore for a second what this means. (Please consult the NCDC chart below.) January 2009 continued a run of several decades in which January temperatures were always higher than the long-run average. Although January seemed very cold in the UK, for the world the land and ocean temperature was higher than any year in the entire twentieth century, although some years in the 1940s came close.

The plain fact is that UK commentators have simply lost touch with what winters used to be like. The climate change deniers base their refreshed scepticism on a few weeks of recently unprecedented snow and ice in the UK. They do not either look at records in the rest of the world, or consult historical data on UK temperatures.

These high global temperatures occurred during La Niña Pacific conditions. In an year of full El Niño when Pacific ocean temperatures are higher, we could expect an even warmer climate.

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The sceptics have also written extensively about what they saw to be an extremely cold northern-hemisphere winter. The Sunday Telegraph commentator Christopher Booker called it ‘the winter from hell’. To those unconvinced by the man-made climate change hypothesis, this is further evidence that climatologists don’t understand how CO2 affects temperature.

Both UK and US sceptics are too influenced by climatic conditions in America. Although parts of the United States did have an unusually cold winter, global temperatures have been high.

Here is the summary from the US National Climatic Data Centre of northern winter averages:

The combined global land and ocean surface temperature was the 16th warmest on record for the December 2007-February 2008 period (0.58°F/0.32°C above the 20th century mean of 53.8°F/12.1°C). The presence of a moderate-to-strong La Niña contributed to a boreal winter and February temperature that were the coolest since the La Niña episode of 2000-2001.

Although the period was the ‘16th warmest’, it was still the coldest for several years. But March was very much warmer. Here is what the NCDC says about this month:

The global surface (land and ocean surface) temperature was the 2nd warmest on record for March in the 129-year record, 1.28° F (0.71° C) above the 20th century mean of 54.9° F (12.7° C). The warmest March on record (+1.33° F/0.74° C) occurred in 2002.

The global land surface temperature was the warmest on record for March, 3.3° F (1.8° C) above the 20th century mean of 40.8° F (5.0° C). Temperatures more than 8° F above average covered much of the Asian continent. Two months after the greatest January snow cover extent on record on the Eurasian continent, the unusually warm temperatures led to rapid snow melt, and March snow cover extent on the Eurasian continent was the lowest on record.

Without the continuing (but weakening) La Niña event, the global average sea and land temperature would almost certainly have been the warmest on record in March. 1998 was an extreme anomaly, with temperatures in the US over 1 degree C higher than the previous year. This was driven by a strong El Niño and there is no reason to suppose that the next El Niño event will not produce an even higher temperature.

Climate change sceptics need to get out more. April snow in southern England or in New York does not mean climate change has stopped. Any talk of ‘stabilisation’ is premature.